P - k-Multiple Free Set

P - k-Multiple Free Set

Time Limit:2000MS Memory Limit:262144KB 64bit IO Format:%I64d & %I64u
Submit

Status
Description
A k-multiple free set is a set of integers where there is no pair of integers where one is equal to another integer multiplied by k. That is, there are no two integers x and y(x < y) from the set, such that y = x·k.

You’re given a set of n distinct positive integers. Your task is to find the size of it’s largest k-multiple free subset.

Input
The first line of the input contains two integers n and k (1 ≤ n ≤ 105, 1 ≤ k ≤ 109). The next line contains a list of n distinct positive integers a1, a2, …, an(1 ≤ ai ≤ 109).

All the numbers in the lines are separated by single spaces.

Output
On the only line of the output print the size of the largest k-multiple free subset of {a1, a2, …, an}.

Sample Input
Input
6 2
2 3 6 5 4 10
Output
3
Hint
In the sample input one of the possible maximum 2-multiple free subsets is {4, 5, 6}.

---

1. 题意：
2. 思路：
3. 失误：
4. 代码如下：

#include<cstdio>
#include<cstring>
#include<algorithm>
using namespace std;

const int MAXN=1e7+10;
long long  a[MAXN];
bool flag[MAXN];

int main()
{
    long long   n,k,i,ans,pos;
    memset(flag,false,sizeof(flag));
    scanf("%lld%lld",&n,&k);
    for(i=1;i<=n;++i)
    {
        scanf("%lld",&a[i]);
    }
    sort(a+1,a+n+1);
    ans=n;
    for(i=1;i<=n;++i)
    {
        if(!flag[i])
        {
//          a[i]~a[n] 
//          a[i+1]～a[n] a[i]*k k=1 
            pos=lower_bound(a+i+1,a+n+1,a[i]*k)-a;//原来如此呀，找到的数不能包括自己，如果k=1,也不去除 
            if(pos>=n+1)  continue;
            if(a[pos]==a[i]*k)  
            {
              flag[pos]=true;
                --ans;
            } 
        }

    }
    printf("%lld\n",ans);
    return 0;
 }